1. Field of the Invention
This invention relates to a process of removing H.sub.2 S, CO.sub.2, COS and mercaptans from gases by absorption in an absorbent solution which is circulated between an absorbing zone and a regenerating zone and contains at least one organic base in an organic solvent in which the gaseous constituents to be removed are physically soluble, wherein the absorption is effected under a pressure of 1 to 180 bars and at temperatures of 5.degree. to 80.degree. C.
2. Discussion of Prior Art
Before natural gases or gases produced by the gasification of carbonaceous substances are used, the acid or sulfur-containing constituents of the gases must be removed. This is preferably effected by scrubbing the gases with suitable absorbent solutions. Particularly if such gases are to be used in catalytic reactions, such as the synthesis of methanol, only very low residual contents of sulfur compounds are often permissible if a deterioration of the catalysts is to be avoided. It is particularly difficult to remove carbon oxysulfide (COS), because it has only a low reactivity at normal temperatures and has a low solubility in the usual physically acting organic solvents, such as methanol. For this reason, relatively large quantities of the absorbent solution are required for removing the sulfur compounds, particularly COS, to a high degree. This involves a relatively high expenditure for equipment and supplies, such as electric power and steam.
It is known that the absorption of acid gases and organic sulfur compounds, e.g., in methanol, can be improved in that 0.2 to 4 moles/liter of an ethanolamine is added to the methanol (German Pat. No. 1,815,137). But this results in undesired secondary reactions of the ethanolamines with formation of compounds which cannot be thermally regenerated. These byproducts must be removed from the absorbent solution with an additional expenditure, e.g., as distillation residue, if a constant scrubbing action is to be maintained and corrosion is to be avoided.
It is an object of the invention to avoid these and other disadvantages of the prior art.